Models of the Heart
by NightSpear
Summary: The SGC scientists learn, over time, how to model Goa'uld circulation. Sam considers a few things in the meantime. Spoilers for seasons 1-8.


Disclaimer: Nothing you recognize is mine. I gain nothing of material value from this.

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Models of the Heart  
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I. Anatomical Model

Structure and function were linked. Sam was pretty sure the first time she had heard about structure-function relationships in class had been her high school biology course, but it held true outside of biology, too--sometimes, one simply had to dig deeper or use a stronger microscope to see the structural features that determined function, but it was still a fact that if something happened, as far as she was concerned, there had to be a physical basis for it.

"The problem is that we don't always understand the link between anatomy and physiology," Janet said idly as she sliced through one of Hathor's spawn, carefully and methodically removing the larval Goa'uld's internal organs as Sam looked on and tried not to make faces while listening to squelching sounds. "And it's dangerous to assume that there's a direct one-to-one correlation that can be applied to--ooh."

"Ooh, what?" Sam said leaning closer despite herself. "Is that..._blue_ blood? Colonel O'Neill saw a symbiote get crushed on Chulak before Rya'c's implantation--I'm pretty sure he would've mentioned it if the blood had been this blue."

"I've drawn small amounts of blood from Teal'c's symbiote, and it was always clear to blue," Janet said, looking even more interested now. "I can ask him about it, though. Didn't Dr. Jackson say something about host DNA being used for compatibility?"

Sam suppressed a wince, remembering Daniel's expression when she had found him after Hathor had...well.

Instead, she thought about what would change the color of blood, then said, "That's right. It's the iron that makes blood red, right? Bound by, uh, hemoglobin. So if the host DNA--"

"Or even the developmental stage of the symbiote," Janet added, "or other environmental factors."

"If _something_ affects which genes are expressed, different symbiotes in different situations might product different proteins that bind different ions. Copper, maybe?"

"Hemocyanins are used by some organisms on Earth," Janet told her, "especially ones with less developed circulatory systems. They use copper as the main oxygen carrier, and they have different binding affinities to oxygen that make them more ideal for respiration in environments with low oxygen pressure. Teal'c's symbiote definitely seems to utilize much more copper than iron, compared to humans."

"Where's this one's heart?" Sam asked, peering at the viscous, blue fluid inside the larva on the table.

Janet pointed to a pile of blue goo.

"Oh," Sam said. "That's...a heart?"

"Mm-hm. I'd expected it to be similar to, say, reptilian hearts on Earth, but this circulatory system is...quite different."

"It's still a pump, right?" Sam said. "It does the same thing--circulates blood and oxygen."

"Oh, it's still a pump," Janet said. "But that's just what it _does_. I'd like to know why and how it does it--it almost looks like there's an extra chamber in here, and I'm not sure I'd label them as anything like atria and ventricles. It's too bad we couldn't observe it in action, and I'm reluctant to conduct too many tests on Teal'c without understanding more about how to keep Junior healthy. Sam, could you..." She pointed to the next bench.

Sam handed the scissors over and watched her friend gingerly turn the heart apparatus over to look at it from all angles.

"You know those heart models--the colored, plastic ones they have in classrooms that you can take apart?" Sam said. "They never seemed to explain much, other than what to label parts on the anatomy portion of the final exam."

"There's a lot you can't tell just by looking at one of those," Janet agreed. "But that doesn't make them useless. Function follows structure. The problem is that we don't have models so exact that we could infer every function from structure, nor do we understand biology well enough to make those deductions even if we _had_ perfect models."

"But not every physical feature of an organism serves some useful function."

"No?" Janet said without looking up. "You want to be careful with that assumption--someone might prove you wrong five years down the line. We thought that about the appendix for a long time, and now we're starting to find that it might have some function after all, even though it doesn't seem essential for survival in an adult."

"I think I've read something about that," Sam said. "All right. But still, the amount of detail you'd need to be able to deduce every single function from anatomical features..."

"Pretty astronomical, yeah. And it might not be worth the effort to get so much detail, which, in any case, wouldn't describe the amount of variation seen from one individual to another."

"It's the Medical Uncertainty Principle," Sam joked. "It is impossible for a model to tell both everything about a single organism and also enough about all organisms at once."

Janet laughed. "Actually, the 'medical uncertainty principle' refers to uncertainty in diagnosis and treatment of any given patient or condition."

"There's actually a _principle_ for that?"

"Well, it's what we called it in med school."

"I say that sometimes you just need to plug it in and see what it does," Sam said.

"There's a time and a place for empirical treatment, Captain," Janet said, still smiling.

When Janet stuck a pin in one corner of the heart and another into the larva, Sam asked, "What's that for?"

Janet looked up and raised an eyebrow. "Making sure I remember which wire goes with which socket."

...x...

Sam found Teal'c at the shooting range. He was there or in the gym a lot--he didn't have a lot of official duties other than missions with SG-1 and handing in reports afterward, but the personnel had begun to warm to him and seek him out for instruction on Goa'uld language or combat techniques.

"Hi, Teal'c--may I join you?" she asked when he paused and seemed to be studying an M9 pistol in his hands.

"You may indeed, Captain Carter," Teal'c answered formally. He took a step to the side, as if expecting her to join him in his lane, then moved back, perhaps unsure of what the protocol was.

One day, Sam promised herself, she would get Teal'c to call her something that made them sound like teammates who spent far too much time together, not coworkers who kept a strictly-professional distance at all times.

"Have you seen Colonel O'Neill or Daniel today?" she asked, moving toward him to examine the array of firearms he had on the counter.

"Indeed."

"I didn't see them come in. Are they...did they seem..." She grimaced, not completely sure of whether she should approach them to ask how they were dealing with the Hathor incident. "Did they seem okay?"

"They arrived at the SGC while you were assisting Dr. Fraiser in her butchering," Teal'c told her, "and they did appear to be well."

Sam looked up, startled. "_Butchering_?"

Teal'c tilted his head. "Is that not the correct term, Captain Carter?"

"Uh...no, not really," she said, wondering who the hell had told him that one. On second thought, it had probably been O'Neill, who would have used the term casually to describe a dissection. "She was _dissecting_ symbiotes."

"I see," Teal'c said, his expression not revealing whether he saw or not.

A thought struck her. "Have you ever seen the inside of a Goa'uld symbiote?"

"Jaffa are, on occasion, publicly punished by having their symbiotes extracted and crushed," Teal'c said calmly.

Appalled, Sam found herself with her hand half-extended, as if in some sort of reflex to pet Junior and assure it that no one was going to crush it. She pulled it back when she remembered that that would involved taking off a teammate's shirt and sticking her hand inside his abdomen, not to mention petting a Goa'uld. "That sounds...horrible," she said instead.

"It is quite painful," Teal'c added.

"I can imagine. By the way," she said, "that's not what we were doing. A dissection is a little more...controlled than that. More like..." She picked up the MP5 next to the pistol. "Like field-stripping a gun to see what's inside and to understand its mechanics."

Teal'c seemed to consider that, then reached out and disassembled the pistol, laying its pieces neatly on the counter. "This does not aid in discerning a weapon's purpose," he said.

_Weapon Anatomy 101_, Sam thought. Teal'c could manipulate most weapons as well as or better than anyone else on base, but she doubted that anyone had bothered to explain more than the basic workings to him, nor that he would have asked. She suspected it was part of Jaffa training--Teal'c had told her exactly how much of what kind of damage could be done with a staff weapon used in each of ten different ways, but he hadn't had the first clue when she'd asked him how it worked.

Then again, a lecture on the variations of firing pins and actions was probably better suited for another venue. There were other aspects much easier than that to demonstrate.

"Actually, there's a lot you can learn about a weapon's purpose," Sam said, easily reassembling the pistol. "Can you take that one apart, for example?" She pointed at a staff weapon.

"It is forbidden for a Jaffa to damage his weapon," Teal'c said, the response sounding almost automatic. It probably was, in a way, after having rules drilled into one's head for nearly a hundred years.

"Well, staff weapons are designed so that they can't be easily disassembled without damaging them, at least without tools," she pointed out. "The guns _we_ use are designed so that they _can_ be taken apart quickly if needed."

Teal'c nodded once. "Your warriors are more trusted by their superiors than are Jaffa."

Sam looked up at him out of the corner of her eye. She had already drawn that conclusion for herself. Aside from their brushes so far with the Goa'uld and their Jaffa, she had watched Teal'c closely over their first several missions and noticed how puzzled he had first seemed when Colonel O'Neill had given him a weapon and then casually turned his back, or how Teal'c obeyed orders even when he clearly had no idea why or even what they meant. She wasn't sure yet if that had been part of his training or if he simply thought he wasn't allowed to ask questions.

"Probably," she agreed. "Also, Goa'uld weapons don't jam or need maintenance as often as Earth weapons." The Goa'uld might be lax about Jaffa safety, but keeping their armies at full efficiency was good for their chances of victory, too. She picked up a staff weapon. "Honestly, though," she added, "and no offense intended, but I can't see the reasoning behind this design. Maybe I'm not holding it right or I need more practice, but it's not nearly as easy to support and balance a staff weapon as it is to couch a submachine gun under your arm."

Then she glanced up again, considering the differences between Teal'c's body and her own. Even an average Jaffa warrior, through training and genetics, was significantly stronger than the average Earth-born groundpounder. Even if it seemed inefficient, it was quite possible that Jaffa _were_ able to support a staff weapon better than she could, just on raw muscle strength and control alone. Still, the weapons could be used much more efficiently if it were designed better. Sam imagined making the staff weapon more compact--Teal'c could probably hold one in each arm, then.

And even Teal'c said, "I have found that your weapons allow greater precision than those that I am accustomed to using."

"Yours make a bigger 'boom,' though," she offered, and then, "Oh, hey, that's a good point!"

"It...makes a bigger boom," Teal'c echoed, a little dubiously.

"A scary one," Sam clarified. "Right? I mean, if I hadn't known the shape of a gun all of my life growing up, I might not think it was a dangerous weapon just by looking at it. But a staff weapon...I'd duck away from an armored warrior threatening me with a large, metal rod, even before I saw the fireball it spat out."

"To carry a staff weapon is a mark of authority," he agreed.

Function followed structure. The staff weapon's odd design didn't break that rule; it just didn't serve the function Sam had originally assumed. "It's made to intimidate," she said. "Obviously, it kills, too, but that's only half of it."

In fact...Jaffa warriors spent a lot of time in battle against rival armies, but they spent a lot of time supervising frightened slaves, too. When Abydos had freed itself from Ra, they had had the help of the US Air Force, but they had also proven what would happen if all slaves rose up against their masters. At some point, numbers would overwhelm technology. Fear kept uprisings down more than anything, and so Jaffa weapons were designed to inspire fear.

Teal'c was looking more thoughtful now, as well as a little torn. He practiced with just about every weapon available on the base and was pretty close to an expert in all of them now, but he was still partial to staff weapons. Sam supposed a lifetime of habit was hard to break, and she wasn't going to deny that there were real advantages to staff weapons, too. Bra'tac, in particular, had been quite fond of--and quite deadly at--using his as something like a quarterstaff.

"This is a weapon of war," Teal'c said.

"But it's also a weapon of terror," Sam said.

"There are times," he said, "when terror is the objective."

"I guess so," she said, making a face. "But sometimes it's not."

"Indeed," Teal'c said, and he picked up the submachine gun to continue practicing.

II. Multi-Compartmental Model

"Obviously, the compartments can't be homogeneous," was Janet's first remark.

Sam paused in her explanation.

"So we're thinking of Junior as this compartment here"--Janet pointed to a box on Sam's diagram--"and this arrow indicates some nutrient A entering Junior from the environment of Teal'c's abdominal pouch. Right?"

"Right," Sam said. "Or, actually, the compartment is just its circulatory system. We'd need other parameters to describe the passing of nutrient A from its blood vessels and to other tissues."

"But the point is, that means there will be a higher concentration of that nutrient near the interface between the symbiote and the environment compared to the concentration more distant from the interface. And the same is true in reverse for Teal'c if we consider his entire circulatory system as a single compartment."

"Well, yeah," Sam said. "That's one of the limitations of this model--it assumes the compartments are all well-mixed immediately, but we could, in principle, break each one of them down into more compartments, each of which encloses a smaller volume. It's even conceivable to represent each one's circulation as a series of infinitesimally small compartments, which is a lot closer to being true; it just makes the math a little more complex."

Janet raised an eyebrow at her.

Sam had seen her friend make rapid dosage adjustments using back-of-the-envelope calculations with body mass and drug half-life. That had to be based on a compartmental model of some sort, too. "Don't you use some sort of model like that in pharmacokinetics?" she asked.

"Sure," Janet said. "There's a 'volume of distribution' term we use when thinking about where in the body a drug will get, and sometimes, it's considered a well-mixed, homogeneous compartment. But it's thought of that way so we can do quick calculations on the spot. If I find that my patient is being overdosed, I'm not going to take the time to do complex math just to figure out how to adjust the speed of the IV drip. Med school teaches a lot of things; solving a set of differential equations in one's head within ten seconds isn't one of them."

"So this model would still be useful for administering a medication to Teal'c or to his symbiote," Sam summarized. "It might not be the most accurate for all situations, but it's still a useful tool."

"Practically, yes," Janet agreed. "But I'd still like to run more tests to gain better fundamental understanding. There's a lot to be learned about symbiote and Jaffa physiology."

"If only we could ask a symbiote," Sam joked.

Janet smiled ruefully. "If only."

...x...

The first time Sam felt Jolinar's heartbeat, she nearly jumped out of her skin.

Then she felt Jolinar's grim amusement and wished she _could_ jump out of her skin, even as Jolinar was thinking it was a silly, impossible notion. Her skin was her own, except that Jolinar had part of it, too.

_'Get out,'_ she screamed silently. _'I don't want your feelings and your--'_

Jolinar didn't bother answering. He didn't have to; Sam _felt_ and _knew_ as soon as he did, just like she had known the name Jolinar before she had been forced to introduce herself as such to Teal'c. It was as if the two of them weren't two separate compartments but rather a single, well-mixed compartment, the kind that only existed on paper and in theory. It was a simplification and it worked fine for some models, but this was her head, and it was not simple, and she could not be well-mixed with a symbiote, even though she felt when he felt and moved when he moved.

_BLENDED_

_'What?'_ Sam tried to ask. _'Was that...was that you? Are you Jolinar?'_

Something drew back, distancing them, and she felt her body stop moving restlessly around the cell. _'The term,'_ an impatient Jolinar told her, _'is "blending." A symbiote blends with its host. We are not one; neither are we separate. Now be quiet and let me find a way out of this prison.'_

For a moment, Sam was so stunned to be addressed directly and spoken to at all that she stopped struggling for the first time since she had woken up as a passenger in her own body. Then she retorted, _'Then I should keep talking to distract you.'_

Not that they'd get out, anyway. This was a secure cell with sturdy bars, surrounded by security lasers, in a secure room. Without fancy Goa'uld technology and without even access to Tau'ri technology and tools, they were well and truly stuck here.

Briefly, she felt bad for the others. They would have a hard decision to make soon regarding her.

_'You're not getting out of here if I have anything to say about it,'_ she told the symbiote.

A flash of irritation--not true anger, but deep annoyance. _'You have no say,'_ Jolinar said, and disappeared again into a swirl of wordless thoughts and memories and emotions.

They paced agitatedly, searching for cracks that Sam knew weren't there, because she was one of the people who had made sure there were no cracks to exploit from the inside. Jolinar was surprised at the advancements made by mere humans. Sam imagined flipping him the bird and was childishly satisfied when it gave Jolinar pause.

_'How are we connected?'_ Sam wondered.

Disdain. _'We are in contact at countless points along my body and your central nervous system.'_

Revulsion. Sam was fairly certain that was her own. _'That's not what I meant. How exactly are we exchanging electrical signals between your mind and my neurons--what kind of synapses are they? Is there a temporal delay? Do we share hormones and other substances? Is your vasculature connected to--'_

_SILENCE_

Sam mentally staggered back a bit, then recovered. _'When I feel your heart beating, am I feeling it or am I feeling you feel it?'_

Jolinar didn't answer.

They sighed.

Whatever else they exchanged, she was clearly getting something from Jolinar that made her feel...really intense. Like an endorphin rush that kept the mind clear and never crashed. Maybe it was what made Goa'uld so much stronger than humans. So even though her legs weren't tired, Sam tried experimentally to sit down on the ground.

To her shock, she found herself sitting.

She wiggled her fingers. They wiggled.

The surprise reverberated, amplifying. She realized some of it was Jolinar when it reversed direction, becoming annoyed again, and they stood back up and stuffed their hands and wiggling fingers into their pockets.

_'That's real mature of you,'_ Sam thought.

Anger. Desperation. Indignation. Sam couldn't tell which of them those belonged to. _'I do not enjoy holding hosts prisoner,'_ Jolinar said grudgingly.

Disbelief.

_'Do not push me,'_ Jolinar warned.

_'Yeah? What'll you do? Hit me?'_

Silence.

Emptiness.

Nothing.

_'Hello?'_ Sam called tentatively when she couldn't move again and Jolinar seemed to have disappeared. _'Jolinar?'_

_'I do not know,'_ Jolinar said.

Confusion.

_'I have never wondered which of us is the one whom you perceive to feel my heartbeat,'_ Jolinar clarified. _'No host has asked me that before.'_

Surprise.

_'But there is no difference,'_ Jolinar said.

Frustration--Sam's. _'Yes there is,'_ she said. _'I was here first. You have no right to me--my thoughts are mine, and yours are yours, and you have no right to mix them. _Blend_ them.'_

Frustration--Jolinar's, maybe, or maybe hers that he was feeling. _'Do you think this was my choice?'_

_'Well, it sure as hell wasn't mine, and you know it.'_

Impasse.

Despair. Determination.

_'What do you want?'_ Sam said. _'Why are you here?'_

A dizzying whirl of images flew past her--faces, planets, battles--

_'That was another Goa'uld,'_ Sam interrupted, grasping at one of Jolinar's memories that he snatched quickly away. She suspected he hadn't meant for the flood to leak through. _'Why was another Goa'uld torturing you if you're also a--?'_

Fury. _'I am not a Goa'uld,'_ Jolinar snapped.

Sam wondered if Jolinar was perhaps insane.

Jolinar wondered if Sam would like to relive the memory of that torture.

_'Then explain it to me,'_ she said.

_'Why are you speaking to me?'_ Jolinar asked, full of confusion and not a little wonder.

_'Curious.'_

_'Why?'_

_'I'm curious.'_

Jolinar turned her hands over and examined them, rubbing the fingers together and feeling the calluses. He leaned forward and examined the security that surrounded them, not looking for an escape, this time, but rather out of curiosity. _'You designed this,'_ Jolinar said, not a question.

_'I helped,'_ Sam said. _'Not just me. There are lots of good engineers working security.'_

Hope.

_'What do you want?'_ she tried again.

_'To go home. To complete my mission.'_

Sam sat back. She wondered who had told her body to do that and thought that maybe it didn't matter. It made no difference--they had been blended.

_'We've never studied the connection between a symbiote and a host before,'_ she told Jolinar, for lack of anything else to do and because she wasn't going to sit idly and let Jolinar think of a way to escape. _'We know a little about Jaffa and their symbiotes, but this is different.'_

Puzzlement.

_'We've determined that there is no direct connection between the circulatory systems in a Jaffa. None of Teal'c's blood has ever been isolated from his symbiote or vice versa.'_

_'Toxic. Fatal. Their blood cannot mix.'_

_'Yeah, the reaction _in vitro_ was like a really bad graft rejection with toxic side products on top of it. Besides, we can physically remove the symbiote from Teal'c, so they're not connected like that.'_

_'A symbiote's skin is adapted to absorb only the fluids and nutrients it needs,'_ Jolinar said. Sam tried not to react. Jolinar felt her try not to react and did not comment._. 'It also restricts its own blood from reaching the Jaffa's abdominal pouch, where they would be almost instantly absorbed into the Jaffa's bloodstream. Your engineers are not incorrect in using a compartmental model to describe the exchange between symbiote and Jaffa. There are vastly different parameters that apply to the symbiote compartment and that of the Jaffa.'_

Sam wondered how Jolinar knew what their engineers were doing. Jolinar pulled her personnel file out from her memories, just because he could.

_'The exchange between them...it's sort of like a placenta,'_ Sam thought.

Wry amusement. _'But without the placenta,'_ Jolinar said. More haughtily, _'And it is still a very crude model.'_

_'But it's different for us,'_ Sam said. _'Your...your pulse matches mine.'_ Their heart rates spiked together as the realization excited her.

_'This is a closer connection,'_ Jolinar agreed. _'Much closer. I was with Rosha for nearly two hundred of your years.'_

Sudden panic. Panic. _Panic_.

_STOP_

Sam felt their pulses racing as her reality sank in again.

_CALM DOWN CAPTAIN CARTER CALM CALM_

Slowly, the panic receded again, to be replaced with a deep, aching sorrow that she didn't think was her own. She was sitting again. It was impossible to know if she had slid to the ground or if Jolinar had sat her down.

_'Sorry,'_ she thought, and hated that she was sorry for making Jolinar panic. She hated that they were in this together, and she hated Jolinar for making her feel this way, because she wasn't even sure how much of it was her and how much was him.

Silence.

Then, _'Sorry,'_ Jolinar said, and he was, truly, but they both knew it didn't change anything.

Sam sighed again. _'You have a mission,'_ she said.

Determination, steel-hard. The regret faded.

_'Who's Rosha?'_

The face of a woman flashed in front of her. This time, Jolinar didn't rip the image away, but let it linger, showing her. Sharing. _'Host,'_ Jolinar said.

And Sam remembered how Jolinar loved the sea, because Martouf said Rosha's eyes were the color of the seas of his home. _'Who's he?'_ she asked.

The images disappeared behind a wall.

_'I need to get out,'_ Jolinar said. Back to the mission.

Agreement. _'Then get out. I'm not stopping you. You're the one who invaded me.'_

_TOK'RA NOT GOA'ULD TOK'RA_

Resistance. That was what it meant. Jolinar had made her say it already to Teal'c and Colonel O'Neill and Daniel, so Sam didn't have to ask what 'Tok'ra' meant. She still remembered some of the images she'd seen before, though, the ones that had slipped through the cracks between Jolinar's mental compartment and hers, and there had been ones of Jolinar bowing and scraping to a System Lord she didn't recognize--and Jolinar had meant it then.

_'That was long ago,'_ Jolinar said stiffly. _'Not anymore. I defected. Tok'ra now.'_

Sam tried to kick the wall violently with a foot, just so that Jolinar would consciously, forcefully stop her and prove her point. _'Liar,'_ she said. _'Still a Goa'uld.'_

_'No,'_ Jolinar denied. Guilt was seeping in, but his resolve remained strong. Some perverse part of Sam reluctantly respected that will. She should know--she had been trained to fight, too, and knew that choices could be difficult. She supposed it meant something that Jolinar felt bad about it, though it wasn't nearly enough. _'No choice,'_ Jolinar insisted.

_'You had a choice. I didn't.'_

_'There is an ashrak,'_ Jolinar said. _'He will stop at nothing kill me, and then he will try to use me to find the Tok'ra.'_

Sam didn't wonder if it was the truth. Fear was coursing through their veins, and a pounding heart threatened to leap out of her chest (and another pounding heart pulsed against her spine).

_'I would rather die than be used to hurt my people,'_ Jolinar said.

_'You would rather _I_ died, too,'_ Sam had to point out. _'You would rather let Nasyans die than your own people.'_

_'Your people claim to fight the Goa'uld. The survival of the Tok'ra may be the only hope for that victory.'_

_'We could help.'_

_'I did not know of your people.'_

_'You could have asked!'_

Jolinar was torn between impatience and regret. _'There was no time, and you would not have believed me.'_

Sam guessed that was true enough.

_'My people won't let you out,'_ she said. _'Even I don't know enough to trust you. They can't trust you. You understand that.' _

Anger, masking fear. _'I know,'_ Jolinar said. _'But the ashrak will come. I will not let him take me. I will not betray the Tok'ra.'_

_'We could be allies,'_ Sam said again. _'I'm not a tool for you to use. Look--look in my head. You know what we've accomplished in only one year. If you aren't Goa'uld, then we should be allies.'_

Scorn, and then a thoughtful spark of hope. _'Perhaps,'_ Jolinar said, but there was still doubt in it. Some of the doubt, though, was more about the likelihood that the SGC would ever trust her--him--_them_ now, not just skepticism about Tau'ri capabilities. _'When this is over, Samantha Carter, if we survive, then I would like to speak with you more on this.'_

_'I won't give you up to the ashrak,'_ Sam said.

Surprise. Gratitude, shoved back out of the way. _'You have no control,'_ Jolinar reminded her, though he was gentler this time. _'You could not betray us even if you wanted.'_

Resentment. Sam shoved that out of the way, too. _'I just thought you should know,'_ she told him. _'We don't surrender to the Goa'uld, either. If he comes for us--'_

_'When. Not if. When.'_

_'When he comes, I'll be on your side, not his. Just so you know.'_

Jolinar's heart slowed, calming. _'Good,'_ he said stiffly.

Overhead, an alarm blared. The lights flickered out, and then the emergency power flicked back on.

_'He is here,'_ Jolinar said. _'The ashrak has found me.'_

They stood. Sam straightened her spine. Jolinar didn't stop her--or he straightened, but she didn't stop him. They weren't one, and this wasn't her choice, and he had made choices that she understood but would never accept as right...but for now, there was an assassin trying to kill them, and they stood together. "No surrender," they said aloud.

It seemed like only minutes before a beeping noise came. The door opened. Sam didn't recognize the airman who entered, but their hearts skipped a beat, their blood recognizing something wrong about the man, and she knew it was the assassin. It was time.

_'I am on your side,'_ Jolinar told her.

Sam braced herself and listened to their hearts beat.

III. Lumped Electrical Model

There was a comforting simplicity in circuit diagrams. Not that they were necessarily _simple_, to most people's eyes, but electricity followed rules and did not disobey them. Obviously, a circuit on paper assumed ideal wires, not physical wires with physical imperfections, but it was a clean, simple way to look at things. Sam liked circuits. They made sense.

Unfortunately, not everything in the world was that simple.

There was something very strange in representing the elasticity from muscle and structural proteins of a blood vessel as a charging capacitor, or accounting for resistance to flow as electrical resistance, not to mention equating blood flow through a tube as electrical current.

Some of the biomechanical engineers were quite comfortable with the notion, though, and didn't share her instinct to protest that an ideal wire on paper _couldn't_ a good model for an artery that probably had gunk on the sides and cells flying through them. Apparently, the model actually worked pretty well when the parameters were tweaked the right way.

"It's not as if we forget, say, internal resistance in these wires..." Dr. Bennett explained.

"Blood vessels," Sam inserted. "Not wires." Wires were clean; blood vessels were messy.

"I mean on the diagram," Bennett said. "Wires, capillaries, same thing. The overall resistance can be lumped together and accounted for here by resistance element R--varying, of course, depending on factors like neural stimulation or hormone signals--and when you think of it that way, it's not so different from taking the internal resistance of copper wires into account."

Which made sense. Sort of. Mathematically, it made sense, and it _did_ match experimental results if they had good enough initial measurements to go on. Sam just had to stop herself from wincing when she saw a computerized image of a filling, ballooning left ventricle and saw it represented like what she thought of as a parallel-plate capacitor.

"It's just storing blood and plasma instead of storing charge," Bennett said, shrugging. "Compliance, capacitance. Po-tay-to, po-tah-to."

"Yeah," Sam said. She reflected that she'd never actually heard anyone say 'po-tah-to' except when using that expression. "You lump all of the arterial flow into this one segment, then, with one resistor and one capacitor? And the same with the venous flow."

"It's not pretty," Bennett said, "but it works. That's what counts, right?"

Sam had to admit that, if one were looking for efficacy, it was true. "So how do you account for the Jaffa?" she asked.

"We're still working on that," he admitted. "We really don't have enough information to go on--it's not like we have animal models we can use for experiments."

_And we're not allowed to poke too many holes in Teal'c,_ was the unspoken part of the statement. To the man's credit, he didn't even seem to consider making it spoken. Sam wasn't sure if it was out of true respect for Teal'c--a few of the newer scientists rarely interacted with Teal'c and thought of him mostly as an interesting Jaffa specimen--or fear of attracting SG-1's ire.

"All right," she said. "Doctor, send me a copy of this report, please, and if you think of non-invasive--_non-invasive_--tests to run with Teal'c's assistance, make sure we have permission from General Hammond, Dr. Fraiser, Teal'c, _and_ Colonel O'Neill first."

"Of course, Major," Bennett said. "There's something else we've been working on, too, involving one of the neuroactive, biological adhesives found on M89-CJ7 that we've incorporated into an injectable polymeric scaffold. If you'd like to take a look, I believe Dr. Warner is in the process of using it to help in reattaching a rat leg right now."

Sam stared at him. "He's...what?" she said.

"Reattaching a rodent hind limb," Dr. Bennett repeated.

"Why?" Sam asked.

"Because it's...not attached right now," he said, looking confused.

"Did _he_ detach it?"

"Well...yes," Bennett said. "But we think we're able to restore nearly one-hundred percent function now if the procedure is performed within a short period of time. It's better than prostheses, Major. Well, maybe not _yet_, but by the time we get approval to start human trials..."

"Yeah, I'm sure," Sam said. "Uh. Okay. That's more Dr. Fraiser's area than mine, but, uh, send me the cardiovascular model and I'll see if I can find anything that's missing. And...don't detach any human limbs just yet."

"Equivalent circuits to you, surgeries to the medical team," Bennett said, nodding. "Yes, ma'am."

That night, Sam had a dream about plugging Teal'c into a wall socket while they replaced Junior with a mess of wires.

...x...

She woke to the news that Kresh'tar had been attacked, and by the time she, the colonel, and Jonas had dragged Teal'c and Bra'tac back to the SGC, she dearly wished that they _did_ have a mess of wires they could use to replace a symbiote before one of the two Jaffa died.

Or both of them. Junior didn't look like he was going to make it, either.

Jonas was in her lab the first time she stepped out of the infirmary. "Hey," she said, quietly, but he still jumped.

"Sam," he said. "Hey. Uh, I didn't think you'd mind if I looked around at a few things."

"No, of course not," she assured him. "What are you looking at?"

"This," he said, and then, "I thought resistors were the zig-zag lines, not a box."

"It's just the convention--it's like the same word written in different fonts," she said, skimming over what he was reading and recognizing Dr. Bennett's report. "You know, it's funny--I was just talking to Dr. Bennett about Teal'c's symbiote and whether there was anything else we could learn from it."

Jonas glanced at her, then away.

She pulled a stood up to the bench and sat beside him. "He'll be okay," she said, patting Jonas once on the back. "Teal'c and Bra'tac both. We'll find something--we always do."

"Stick some wires in their pouches to act as a shunt?" Jonas said, nervously lighthearted as he pointed at the equivalent circuit Bennett had drawn out to represent the symbiote's circulatory system. "Tubes, maybe?"

Usually, Jonas was the one who looked on the bright side, but he wasn't used to seeing his teammates in this kind of peril yet. Even when the colonel had been taken prisoner by Ba'al, there had been work to do, and most of the other times, they had all been in danger together. This time, Teal'c was lying on a hospital bed, sick with something they couldn't cure, and there was nothing to fight and no research to be done to save him. "Maybe we'll hold off on these," she said lightly, tapping a neatly-ordered box of spare resistors and capacitors. "But the concept isn't a bad one--when you can't directly use or manipulate your object of interest, you find something else that can replace or represent it."

Jonas was quiet for a moment. Then, "We haven't been able to isolate the substances that keep a Jaffa and his symbiote alive. Hard to replace something you when you don't even know what you're trying to replace."

"Well, we've picked up a trick or two in the past few years," Sam said, though they both knew those tricks had more to do with antimicrobial dosages that would ward off illness in a Jaffa than anything else. It was a short-term fix, even if they disregarded the fact that both Teal'c and Bra'tac were injured and had been lying in damp dirt and blood splatters. Without an immune system, all the antimicrobials in the world wouldn't save them from even immediate infections. "And I'm sure the Tok'ra know a lot more than we do."

"Have we heard back from them?" Jonas asked, looking up in excitement.

"Not yet," Sam said, "but we will. My dad's pretty fond of Teal'c and Bra'tac--he wouldn't let anything happen to them."

"Janet's pretty fond of them, too, but that won't help if there's nothing to do."

"Hey, c'mon," she said, bumping his arm. "What's going on? You're not giving up on them already, are you?"

Jonas grimaced. "No. Sorry. It's just...what if we'd gone to check on them sooner? Or what if we'd gone _with_ Teal'c from the start?"

"Teal'c needs to distance himself from us once in a while," Sam answered promptly, as if those same questions hadn't been turning over and over in her own mind. "If we'd gone with him, we'd look more like his handlers than anything else, because if the colonel gave an order, Teal'c would have to follow it, which wouldn't look good at a meeting like that. If the rebel Jaffa start to worry that the SGC is looking to take the System Lords' place, we'll lose them as allies, too."

"And now they're dead, so we've lost them anyway, permanently," he pointed out.

Sam sighed. "We didn't know that would happen. And we went to check on them as early as we could have without knowing something had gone wrong. This was a diplomatic matter. You know how carefully it had to be handled."

"Yeah," he conceded. "I know. Still. I wish--"

"Yeah," she said. "I know."

A moment later, Jonas said, "I wonder how many things in life we could model as electrical circuits?"

Sam was surprised by a short breath of laughter.

"No, seriously, that'd be cool, wouldn't it?" Jonas said, grinning. "Like...the wires are the chain of command. The flow of...orders and commands is current."

"General Hammond can be the voltage source, then," Sam put in, feeling silly and a bit guilty that she was finding this fun, "and Colonel O'Neill...could be the capacitor that stores the orders and then discharges them among us?"

"Eh," Jonas said.

"A little weak on that one," she said.

"Little bit," he said, laughing aloud. "Okay, so not everything fits that well."

Of course not. One of the reasons that the model was incomplete was that there were variable elements sprinkled throughout their diagram of the Goa'uld circulatory system, and they knew precious little about what made each element vary and how. If they knew more about nutrients, hormones, neural signals, stressors, they could fill in a lot of the gaps. Then again, if they knew all of those things, they could provide all of those signals and substances exogenously, and Teal'c and Bra'tac might not be dying now.

"Well," Sam said, "never forget that these"--she pointed to the diagram--"are ideal wires and ideal circuit elements. Real elements are always a little more complicated. But there are limitations that models of the ideal can't overcome, and that's where we get to think outside the box."

_"Incoming traveler,"_ Sergeant Harriman announced over the PA. _"SG-1 to the embarkation room."_

"Or call for backup," Jonas added. "That's the Tok'ra, right?"

"I'm sure it is," Sam said, standing up. "C'mon. Let's go see what my dad has for us."

IV. Empirical Model

Sam wasn't sure what was wrong the first time she hugged her father when he came to meet her fiancé. She dismissed it soon enough, but it stayed buzzing in the back of her mind. When he decided to go to bed early, claiming tiredness, the buzzing became just a little bit louder.

Then, he got her sent off to pick wedding flowers in the middle of a galactic crisis--_in front of her commanding officer_--and her blood pressure drowned out the buzz.

It wasn't until she was standing, frozen, at his bedside in the infirmary that she realized what had been wrong.

A symbiote's heart was positioned along the spinal column, so entwined with its host that it was nearly unnoticeable to any who weren't the host. Over eight years of experience at the SGC, however, had shown Sam a few things, and having a father among the Tok'ra had taught her to find what felt like an extra pulse point at the back of the neck. It was too weak to be apparent to people who weren't looking for it--or who didn't have vivid memories of how that pulse point felt from the inside--but it had always made her jump in the beginning. She had learned to feel it when she hugged her father, at first so that she could mentally catalogue it and accept it and dismiss it, but later because it had become a part of him. They could explain what she was feeling with models and diagrams on paper, but sometimes, experience were enough. That heartbeat was part of a Tok'ra. Sam had observed it and knew it to be true.

This time, she hadn't felt it. Something was wrong.

And then--"It's Selmak," her father said. "He's dying."

...x...

There was really no logical reason to fish at a fishless lake.

Moreover, there was no logical reason to enjoy the activity, and yet, it was what Jack was clearly doing, lounging in his chair, humming softly and off-key, holding his fishing line steady in the fishless lake.

Sam had learned, however, that logic did not always walk hand-in-hand with Jack O'Neill's actions. Rather, his logic was not always the same as hers--but she followed it nonetheless because she followed him, just as he trusted her explanations full of words he didn't know because he trusted her.

Teal'c was still a little grumpy, though. There might not be fish, but there were a heck of a lot of mosquitoes. He wasn't fond of being constantly bitten. Every once in a while, when Jack wasn't looking, Sam turned to give Teal'c a grin, mostly because she thought it was funny to see him sigh and roll his eyes.

This wouldn't have been Daniel's holiday of choice, either--of course not; who but Jack picked fishing at a fishless lake for relaxation?--but he was...contemplative. She guessed that made sense, given that he'd just come back from another trip to the higher planes. At least, this time, he didn't seem _different_ from when he'd left. He hadn't been the last time, exactly--Daniel was still Daniel--but after the fog of amnesia had cleared, the edges had been sharper and more jagged than she remembered. At least this time, all of them had come back home whole.

Ancients were fascinating, in many ways, but their existence and history unnerved Sam, too, because they didn't make sense. People couldn't turn into glowing streams of energy and reside on separate planes, and it certainly couldn't happen through years of contemplation or spontaneous evolution, except that it _could_ happen. She understood it, sort of, in a vague sense, but it defied anything she could explain in a way that really fit science as she knew it. All she knew was that she had seen it with her own eyes, more than once, and she couldn't deny data just because it did not fit her current model.

It wasn't always like that, though. Most of the time, she knew what was around her--they were who they were, and she knew them. Jack made irreverent jokes and tasteless comments (usually in front of high-ranking officers or diplomats) but could hold her in silence when she lost Janet or her father. Teal'c was their rock who shared his private jokes with them using tiny smirks and a glance out of the corner of his eye. Daniel talked too fast about things that seemed utterly unimportant and unrelated, until he explained it and it suddenly became the missing piece Sam needed to complete simulation A in experiment B.

It was the little moments she was wary of--when Jack froze, just for a split-second, as someone gave a report on Ba'al, or when Teal'c's logic faded in the face of vengeance, or when Daniel looked torn between grabbing a priceless artifact and running for his life and he picked up his gun instead.

Sometimes Sam wondered what they thought of her.

"Remember how I used to keep trying to get you to call me just 'Sam' or 'Carter' or some nickname in the beginning?" she said aloud, swiveling around in her chair again to see Teal'c. She used to think it was overly professional, not at all what close teammates should call each other. Now, after all they had been through, she knew that a 'Colonel Carter' from Teal'c could be as gentle or joking or sharp or respectful as any nickname, just as she would never call Jack by his first name--at least, not at work--but she could tell him whatever she needed to with a 'General O'Neill.'

Teal'c raised his eyebrow. "Indeed," he said. "Should I begin to call you Sammy?"

Daniel laughed, snapping out of his quiet to join them. "Yeah, I don't think so," Sam agreed, meeting Teal'c's smile. Her father had called her that before, when she had been little. The reminder that he was gone forever thudded dully against her chest, and she busied herself with the fishing line again. The others were silent, too, because they would have noticed as soon as she'd thought about it.

"So what now, do you think?" Daniel spoke up eventually, when the sky was beginning to darken as the sun began to set.

_'What now,'_ indeed. The remaining System Lords were little more than a joke, the Replicators were gone (from this galaxy, at least), and Anubis was...well, gone for a long time. Sam didn't know how much stamina Ascended beings like Oma had, but whatever fight they were having now would probably last so long that there was nothing they could do about it. What now?

"I was thinking barbecue," Jack said.

Daniel opened his mouth, then closed it. They had all played this game too many times not to know how it worked. Sam caught his eye and shrugged minutely, tilting her head at the lake to say that it would get them away from fishless fishing, at least. "I'm hungry, sir," she offered.

"As am I," Teal'c said immediately. He slapped a mosquito rather viciously.

"Yeah," Daniel said. He shrugged. "Okay, I'm game. Who's cooking the fish? Oh, wait, we didn't catch any." Sam grinned.

"Just for that, you get last pick of the food, Daniel," Jack warned. Daniel didn't look impressed.

When they were all sitting again, this time with a meal and no fishing rods, Sam looked around as Teal'c dug into one of Jack's beer-seared steaks, looking at the first stars of night, and Daniel picked an argument with Jack, seemingly for no reason at all except so that they could argue. In the end, it was what mattered, more than zats and Ancient artifacts--the Stargate had brought them together, but what bound them to each other now was more than that, even with the general no longer part of SG-1 and Teal'c starting to think about the rebel Jaffa and Daniel dreaming anew about Atlantis while Sam dreamed about a galaxy _really_ free from the Goa'uld.

As far as one could get from an SG mission, out of uniform, with gear and weaponry far from reach, this was still who they were, and all Sam could think was that this, here, just the four of them together and doing nothing, was their heart.


End file.
